1. What kind of pressure should the transmitter measure?
First, determine the maximum pressure to be measured in the system. Generally, a transmitter with a pressure range approximately 1.5 times larger than the maximum value should be selected. This is primarily because many systems, especially in water pressure measurement and processing, experience peak values and continuous irregular fluctuations. These instantaneous peaks can damage pressure sensors, and sustained high pressure values or slightly exceeding the transmitter's calibrated maximum will shorten the sensor's lifespan, while also reducing accuracy. A buffer can be used to reduce pressure spikes, but this will slow down the sensor's response. Therefore, when selecting a transmitter, the pressure range, accuracy, and stability must be fully considered.
2. What kind of pressure medium?
Viscous liquids and slurries can clog pressure ports, and solvents or corrosive substances may damage the materials in the transmitter that come into direct contact with these media. These factors will determine whether to select a direct-release membrane and the materials that come into direct contact with the media.
3. What level of accuracy is required for the transmitter?
Factors determining accuracy include nonlinearity, hysteresis, non-repeatability, temperature, zero-point offset, and the effect of temperature. However, nonlinearity, hysteresis, and non-repeatability are the main factors; the higher the accuracy, the higher the price.
4. Temperature range of the transmitter
Typically, a transmitter will be calibrated with two temperature ranges: the normal operating temperature range and the temperature compensation range.
The normal operating temperature range refers to the temperature range within which the transmitter can operate without being damaged. If the temperature exceeds this range, the transmitter may not meet its performance specifications.
The temperature compensation range is typically a smaller range than the operating temperature range. Within this range, the transmitter will certainly achieve its expected performance specifications. Temperature affects the output in two ways: zero-point drift and full-scale output. For example, the +/-X%/℃ of full scale, the +/-X%/℃ of the reading, the +/-X% of the full scale when outside the temperature range, and the +/-X% of the reading when within the temperature compensation range. Without these parameters, uncertainty in use will result. It's crucial to determine whether the change in transmitter output is caused by pressure or temperature variations. Understanding the effects of temperature is one of the most complex aspects of understanding how to use a transmitter.
5. What kind of output signal is needed?
mV, V,
The choice between mA and frequency digital output depends on several factors, including the distance between the transmitter and the system controller or display, the presence of noise or other electronic interference signals, whether an amplifier is needed, and its location. For many OEM devices with short distances between the transmitter and controller, a transmitter with mA output is the most economical and effective solution.
If output signal amplification is required, it is best to use a transmitter with built-in amplification. For long-distance transmission or in the presence of strong electronic interference signals, mA-level output or frequency output is preferable.
In environments with high RFI or EMI, in addition to selecting mA or frequency output, special protection or filters should also be considered.
6. What excitation voltage should be selected?
The type of output signal determines the choice of excitation voltage. Many amplifier transmitters have built-in voltage regulators, thus offering a wide power supply voltage range. Some transmitters are fixed-configuration and require a stable operating voltage. Therefore, the available operating voltage determines whether to use a sensor with a regulator. When selecting a transmitter, both the operating voltage and system cost must be considered.
7. Is an interchangeable transmitter required?
Determine whether the required transmitter can be adapted to multiple systems. This is generally important, especially for OEM products. Once the product is delivered to the customer, the cost of calibration can be substantial. If the product is highly interchangeable, then even changing the transmitter used will not affect the overall system performance.
8. The transmitter needs to maintain stability after the timeout period:
Most transmitters will "drift" after prolonged operation, so it is essential to understand the stability of the transmitter before purchasing. This advance preparation can reduce various problems that may arise during future use.
9. Transmitter Packaging
The transmitter's packaging, especially its rack, is often overlooked; however, its shortcomings will gradually become apparent during later use. When purchasing a transmitter, it is essential to consider the future operating environment, humidity levels, installation method, and whether there will be strong impacts or vibrations.
10. What kind of connection is used between the transmitter and other electronic equipment?
Is a short-distance connection necessary? If a long-distance connection is used, is a connector required?
